In general terms, the invention concerns an optical switch, which in particular can represent a high-resolution colour display. With its colour and polarisation effects, the optical switch is not limited to the visible spectral range. There is also the possibility of light-intensity control in the UV and IR ranges as well as combinations with applications in the visible spectral range.
Liquid crystal displays (LCDs) have long since been state of the art. They are distinguished by a low power demand and robust construction. For articles of daily use liquid crystal displays are used in a big way, being based on the principle that a twisted layer of liquid crystal rotates the polarisation level of light at different strengths according to whether an electrical field is fed or not. The light can then pass through a second polarisation filter in one case and not in the other.
Such a component consists of two glass plates, the support plates, between which the liquid crystal substance is situated. Both glass plates support conductive, transparent electrodes and orientation layers on the inside. When no electrical field is active, the liquid crystal molecules are oriented parallel to the glass plates. On the inside both glass plates support microfine arrangements, which are twisted towards each other (usually by 90xc2x0 or 270xc2x0). Because the liquid crystal molecules align themselves to the arrangements of the orientation layer, a twisting of the molecules towards each other takes place in the liquid crystal layer. If an electrical current is fed between opposing electrodes, this causes an alignment of the molecules in the field direction; the polarisation direction of a penetrating beam of light is no longer rotated.
The structure of a liquid crystal display usually includes two polarisation filters in addition to other components. Each of these filters is aligned on the external surfaces of the support plates, and additional colour filters for colour LCDs. Made up of many layers, conventional LCDs have a very complicated structure. The colour filters are sensitive to high temperatures as they frequently consist of organic polymer material. The light yields in conventional colour LCDs are relatively small in general.
In accordance with DE 42 01 281 A1, a proposal is being made for the formation of substrate plates for liquid crystal displays suited to the colour reproduction of images. This publication sets out the fact that It is usual with substrate plates for liquid crystal displays, the control of which is carried out by means of a dot-matrix electrode structure and which allow colour images, to form the colour pixels of the various primary colours directly onto a support plate. However, as the colour pixels do not form any plain surface contours, they are fitted with a covering layer. The aim is to achieve a further development in this direction in accordance with DE 42 01 281 A1, whereby the colour filter layer formed from colour pixels is covered with an ultra-thin film or layer of glass. This measure is considered necessary if substrate plates are used in displays, which have angles of twist between the liquid crystal molecules of xe2x96xa1 90xc2x0 or which only permit a small distance between the cell plates. As a result of the plain surface, now achieved with the aid of the covering, the aim is to bring about a uniform switching behaviour of the liquid crystal molecules. This example of the state of the art shows what efforts are necessary to produce high-calibre colour displays.
According to WO 94/20879, there is proposed a liquid crystal display, constructed with two support plates made of glass. A liquid crystal substance is located between the support plates. The support plates are provided with transparent electrodes, and polarizers are placed on the outer sides of the support carriers.
Color-structured dichroic filters are arranged on at least one of the support plates, which filters lie within a matrix in the sense of color filter layers and are supported by the support plate or support plates.
Now reference is made to a DE patent application with the reference number 196 42 116.0-33: This patent application, with the title xe2x80x9cProcess for structured energy transmission with electron beamsxe2x80x9d, concerns a process by which energy is transmitted with the electron beam for a short time into limited surface elements onto preferably plain surfaces of objectsxe2x80x94such as plates or tapes made of metallic, semi-conductive or dielectric materials or a combination of them. The useable machining effects are determined by the physical or chemical reaction of the materials to the energy transmission with the electron beam. The preferred area of application is the structuring of surfaces on strip-shaped objects of any length with a limited number of recurring structural elements aligned like a matrix in columns and rows. The essential inventive characteristic of the aforementioned patent application consists in the fact that the object to be machined is moved during the energy transmission contactlessly under a mask, in such a way that an electron beam is guided in the object""s direction of movement oscillating at high frequency approximately vertical to the object""s direction of movement over the recesses in the mask at a very high speed in relation to the object""s movement.
One advantageous area of application is the highly productive structured machining of objects with relatively large surface areas. In the area of thermal electron beam machining the process can be used among other things for the colour structuring of suitably sensitised glass surfaces. For example, in this way a substrate made from glass with a specially prepared thin surface layer can be fitted by electron beam machining with a colour pattern in a repeated structure, as is common in LCD technology for instance. In order to achieve the desired optical effect, four pixels, aligned in an orthogonal matrix in each case, are to be subjected to varying energy densities. During machining a thermal effect causes the thin, prepared surface layer in the areas of the pixels to run through simultaneous temperature cycles, but with different maximum temperatures, in order to obtain certain optical properties pixel by pixel.
With the process in accordance with patent application 196 42 116.0-33, the limits of known processes for energy transmission with electron beams for machining materials have been overcome for the first time. It is now possible to subject structural elements as well as the smallest surface areas, e.g. pixels, to the electron beam defined in a particular alignment on the surface, in order to achieve certain machining effects in this area.
It is the task of the invention to propose an optical switch, which in comparison with known construction solutions has a simplified structure, in which a high light yield and a low parallax is given. The aim is that the optical switch should have a relatively low sensitivity to the effects of temperature as a direct consequence of the solution according to the invention. As has already been stated, the xe2x80x9cProcess for structured energy transmission with electron beamsxe2x80x9d, in accordance with patent application DE 196 42 116.0-33, is currently the latest state of the art. Another task of the patent application submitted here is to use special components, structured according to the process in accordance with DE 196 42 116.0-33, corresponding to the patent application submitted here.
In accordance with the invention, the task is solved as set out in the following, whereby reference is made to patent application 1 regarding the fundamental inventive idea. The other advantageous features result from patent applications 2 to 6.
Further observations are necessary on the solution according to the invention. The support plates of the optical switch, which in particular represents a high-resolution display, consist of glass, into which dichroic colour filters are impressed. These are support plates which were structured according to the process in accordance with DE 196 42 116.0-23. The support plates can have a design that is either plain or not plain. For the structure of the optical switch only one or all support plates, as will be set out, can consist of glass, into which dichroic colour filters are impressed.
The dichroic colour filter layers of the support plates are generally aligned one-sided on the support plates. In the case of special applications the dichroic colour filter layers are to be aligned double-sided on the support plates.
With double-sided dichroic colour filter layers similar or different absorption and polarisation effects can be achieved.
Each of the dichroic colour filter layers in the support plates can be monochrome (monochrome display) or colour structured (polychrome display).
The dichroic colour filter layers are situated inside the glass matrix of the support plates, and they have a matrix-like distribution in accordance with the manufacturing process. The colour patterns in these cases have recurring structures and allow the structure of a display capable of full colour.
The dichroic colour filter layers of the support plates range from the glass surface into a depth of a few xcexcm. To give an indication, depths of max. 10 xcexcm here can be stated. The thickness of the colour zone can here also be only a few tenths of a xcexcm.
The dichroic colour filters have colour and polarisation effects in the visible and/or invisible spectral range (UV, IR range).
To achieve low parallaxes, the structured colour filter layers of the support plates in an advantageous design are aligned on the side which is in contact with the liquid crystal substance, i.e. to achieve the smallest possible distance of the structured surfaces, these surfaces are situated on the inside. In principle, known alignments are being used here, whereby, unlike the known state of the art, the structured support plates in accordance with the process according to DE 196 42 116.0-33 are used.
If the lowest possible parallax is not deemed important, one or both of the colour filters can be situated on the external sides of the support plates, as is the case in principle with the known arrangements and filter structures.
It is essential to emphasise that the colour patterns according to the structuring of the support plates, insofar as they consist of glass, remain stable up to approx. 550xc2x0 C./600xc2x0 C. Other materials should by no means be ruled out here.
As will be explained, transmissive, reflective and transflective structures are possible.
The optical switches (e.g. of the LCD type), to be realised by using dichroically structured support plates, are distinguished by a simplified structure, where in many instances at least one polarisation filter is no longer necessary. The colour filters, dichroically structured, are situated in a layer, obviating the need for additional work with regard to compensating the level of the pixels. The filters are distinguished by a high light yield, as the dichroic filters have a lower basic absorption compared to conventional colour filters.
Some design examples shall explain the invention further.